Current solar central receivers operate at solar fluxes between 300 and 1000 kW/m2, or 30 to 100 W/cm2. The status of advanced solar thermal central receiver technology was assessed by the U.S. Department of Energy in 2012. Two options for significantly improving the performance of solar thermal central receiver technology were identified: (1) using high temperature molten salt, which would allow using a supercritical Rankine power cycle; and (2) developing a sCO2 combined cycle power plant.
The current status of molten salt technology, as represented by the Solar Two molten salt power plant, was assessed by Pacheco in 2002. This particular receiver was producing 565° C. molten salt and had a receiver efficiency of 88%, including absorptivity of 95% and an average flux of 43 W/cm2. Kolb evaluated the possibilities for next generation high temperature molten salt power towers and estimated that currently available receiver technology could operate with an incident flux of about 80 W/cm2. Kolb estimated that with a development effort, this could be increased to 100 W/cm2 with a corresponding thermal efficiency of 94% (or 89% total receiver efficiency, which includes reflection losses based on an absorptivity of 95%). In 2011, Kolb discussed the impact of cyclic stresses and corrosion on receiver design. Kolb also reviewed options for improving the performance and cost of molten salt receivers and concluded that future advanced molten salt receivers would need to achieve operating temperatures of 650° C. and an incident flux of 100 W/cm2.
While a number of papers reviewing sCO2 power cycles were identified, no references are known that provide information concerning the design or evaluation of an sCO2 receiver. The Sunshot program is funding the development of alternative sCO2 receivers, based on published project summaries and presentations at Sunshot Annual Reviews. For example, one new design operates at 750° C. and will use a cavity and a low cost cover glass to reduce thermal losses. A second open receiver design was presented at the 2014 Sunshot Summit, although neither the predicted receiver efficiency for this design nor the incident flux on the receiver surfaces was reported.
Despite these prior and proposed designs, current receiver technology necessary to realize advanced power cycles is insufficiently developed. Accordingly, a need remains for improved receiver technology.